U.S. Pat. Nos. 5,268,147 (the “'147 patent”) and 5,399,497 (the “'497 patent”), owned by the assignee hereof, the disclosures of which are incorporated herein by reference, describe a capsule chemistry sample liquid analysis system which operates through repeated reversible, bi-directional flow of an appropriately configured stream of liquid test packages, each test package consisting of alternating segments of a liquid, such as a sample, reagent or buffer, and air, to enable repeated, precisely timed analysis of the sample of each of the test packages in the stream by one or more sample liquid analysis means. As described in the '147 and '497 patents, the system generally comprises a sample liquid test package metering and supply means which operates to meter successive test packages for reaction and analysis within the system; a reversible direction sample liquid test package displacement means which operates to bi-directionally displace the thusly metered and supplied test packages through the system; a test package transfer means which operates in conjunction with the test package metering and supply means and the test package displacement means to provide for the successive test package supply and bi-directional functions of the system; test package reaction and analysis means for analysis of the thusly supplied and displaced text packages; and detection means operatively associated with the reaction and analysis means to detect and quantify the successive sample liquid test package analysis results. Such a system is particularly adapted to conduct automated clinical analysis of pluralities of human biological sample liquids and can be configured to perform various specific analyses, including well known so called chemistry and immunoassay analyses.
An embodiment of the system just described configured for conducting a chemistry analysis is shown in FIG. 1A. A second embodiment of the system just described configured for conducting an immunoassay analysis is shown in FIG. 1B.
As described in detail in the '147 and '497 patents, the system generally operates by creating a plurality of test packages and successively inserting the test packages into analytical line 30 shown in FIGS. 1A and 1B, which preferably comprises a flexible conduit made of transparent Teflon or like material. The test packages are then repeatedly and bi-directionally flowed back and forth in the analytical line 30 and ultimately past the appropriate test package reaction, analysis and detection means. Depending on the type of analysis being done, e.g., chemistry or immunoassay, particular devices are disposed along the analytical line 30 so as to comprise the reaction, analysis and detection means. As shown in FIG. 1A, a configuration appropriate for a chemistry analysis includes first, second and third flow cells 45 and vanish zone 50 disposed along the analytical line 30. The functionality of these components is described in greater detail both below and in the '147 and '497 patents. As shown in FIG. 1B, a configuration appropriate for an immunoassay analysis includes vanish zone 50, first, second and third bubble detectors 55, first and second magnets 60 and luminometer 65. The functionality of these components is described in greater detail both below and in the '147 and '497 patents.
It will be apparent to one of skill in the art that a test package suitable for a so-called sandwich type magnetic particle-based heterogeneous immunoassay is as shown in FIG. 2. In particular, this test package consists of six liquid segments: a magnetic particle suspension designated as MP, a mixture of sample and first and second reagents designated as S/R1/R2, a first wash designated as W1, a second wash designated as W2, a combination of a third reagent and a fourth reagent designated as R3/R4, and a marker dye designated as D. As illustrated in FIG. 2, each of these liquid segments is separated by an air segment designated as A1/A3, which is a combination of successively metered air segments A1 and A3, or an air segment designated as A2. It will also be apparent to one of skill in the art that other suitable immunoassay test packages exist, for example a test package containing eight liquid segments.
It will also be apparent to one of skill in the art that a suitable test package for a chemistry analysis is as shown in FIG. 3. In particular, this test package consists of three liquid segments: a second reagent designated as R2, a mixture of sample and a first reagent designated as S/R1, and a buffer designated as B. As shown in FIG. 3, with the exception of the S/R1 and R2 segments, each of these liquid segments is separated by an air segment designated as A1, A2 and A3. The S/R1 and R2 segments are separated by a vanish bubble VB comprising air. As described in detail in the '147 and '497 patents, this vanish bubble VB operates in connection with vanish zone 50 shown in FIG. 1A to cause a mixing of the S/R1 and R2 segments at an appropriate time.
Referring again to FIGS. 1A and 1B, the sample liquid test package metering and supply means which creates the test packages described above includes an aspirating probe 10 connected to a service loop 15 which, like analytical line 30, preferably comprises a flexible conduit made of transparent Teflon or like material. Liquid supply 20 is located adjacent probe 10 and generally comprises a plurality of containers for holding and supplying the various liquids to be aspirated into the probe 10 including sample liquids, reagents, marker dyes, magnetic particle suspensions, buffers and washes.
Thus, the test packages just described are created in one or more cycles involving the alternate aspiration of segments of liquid from the liquid supply 20 and segments of air. In particular, with respect to the creation of a sandwich type immunoassay test package, during each cycle, two liquid segments, L1 and L2, and three air segments, A1, A2 and A3, are alternatively aspirated into the probe 10 and up into the service loop 15 by operation of aspiration pump 25, which is selectively coupled to the service loop 15 through transfer line 35 and shear valve 40, to be described below, to create a test package component shown in FIG. 4. The order of aspiration during each cycle to create a test package component is as follows: A3, L2, A2, L1, A1. Thus, a sandwich type immunoassay test package as shown in FIG. 2 is created by aspirating three successive test package components, designated as TPC-1, TPC-2 and TPC-3 in FIG. 2, in three successive cycles. In cycle 1, TPC-1 is aspirated wherein L2 is the mixture of sample and first and second reagents S/R1/R2 and L1 is the magnetic particle suspension MP. In cycle 2, TPC-2 is aspirated wherein L2 is the second wash W2 and L1 is the first wash W1. In cycle 3, TPC-3 is aspirated wherein L2 is the marker dye D and L3 is the combination of third and fourth reagents R3/R4. FIG. 5 illustrates this creation in three cycles. As shown in FIG. 5, adjacent test package components always abut one another at an A1/A3 interface. The chemistry test package, on the other hand, is simply created in one cycle by aspirating a third air segment A3, then the buffer B, then a second air segment A2, then the mixture of sample and first reagent S/R1, then the vanish bubble VB, then the second reagent R2, and finally a first segment A1.
In addition, as described in the 147 and '497 patents, an isolation liquid is aspirated into the probe 10 each time a liquid is aspirated. The isolation liquid preferably comprises an appropriate fluorocarbon or similar liquid, referred to herein at times as oil, which is immiscible with the liquid supplied by liquid supply 20 and wets the hydrophobic inner walls of the system components. As a result, the system component inner walls are coated with an isolation liquid layer which substantially prevent contact therewith by the liquid and the adhesion of the same thereto.
Once the test packages are created, they are transferred to the analytical line 30 for subsequent analysis in the following manner. For an immunoassay using the system shown in FIG. 1B, the probe 10 and service loop 15 is capable of holding a maximum of two test package components. As each successive test package component making up a test package is aspirated into probe 10, the previously aspirated test package component is moved towards the shear valve 40. The service loop 15 is selectively connected to transfer line 35, also preferably comprising a flexible conduit made of transparent Teflon or like material, through shear valve 40. Thus, when the service loop 15 is full, i.e., contains two test package components, and the next successive test package component is aspirated by probe 10, the test package component contained within the service loop 15 nearest the shear valve 40 will move into the transfer line 35. The shear valve 40 is then actuated so as to align the transfer line 35 with the analytical line 30 and, by operation of the aspiration pump 25, the test package component contained within the transfer line 35 is inserted into the analytical line 30. The shear valve 40 is then actuated again so as to realign transfer line 35 with service loop 15 and the next test package component is aspirated. Thus, for each immunoassay test package shown in FIG. 2, it takes three complete actuations of shear valve 40, i.e., a complete actuation meaning from aligning the transfer loop 35 with the service loop 15 to aligning the transfer loop 35 with the analytical line 30 and back again, to move the complete immunoassay test package, one test package component at a time, into the analytical line 30. It will be appreciated by one of skill in the art that if an immunoassay test package containing eight liquid segments as described above is used, it will take four complete actuations of shear valve 40 to move the complete immunoassay test package into the analytical line 30.
For a chemistry analysis using the system shown in FIG. 1A, the transfer is virtually identical except that the probe and service loop are capable of holding two complete chemistry test packages. Accordingly, once the probe and service loop are full, as each successive test package is aspirated (in a single cycle as described above), the test package nearest the shear valve 40 moves into the transfer line 35. Thus, unlike the immunoassay system shown in FIG. 1B which requires three actuations of the shear valve 40 to move a single complete test package to the analytical line 30, in the chemistry system shown in FIG. 1A, each actuation of the shear valve 40 causes a complete chemistry test package to be inserted into the analytical line 30. Accordingly, by operation of the probe 10, service loop 15, aspiration pump 25, transfer line 35 and shear valve 40, appropriately configured test packages are created and ultimately inserted into analytical line 30 for analysis.
Furthermore, for both systems shown in FIGS. 1A and 1B, each time the shear valve 40 is actuated to realign the transfer line 35 with the service loop 15 as described above, stream line 70 is aligned with analytical line 30 and stream pump 46 causes the stream of test packages already contained in the analytical line 30 to flow a predetermined amount or distance in the forward and reverse directions as described in detail in the '147 patents and '497 patents. This flow causes the test packages to successively move through the system and, in turn, undergo appropriate analysis.
Although the preferred embodiment of the present invention utilizes shear valve 40, any inlet valve that is capable of selectively connecting service loop 15, transfer line 35 and analytical line 30 could be used, such as a three-way valve.
As will be known by one of skill in the art, in a typical so-called sandwich immunoassay analysis, the sample S is allowed to react with first and second reagents R1 and R2 within the test package for a particular, fixed period of time as defined by the assay protocol. Then, the magnetic particles are transferred out of the magnetic particle suspension MP and into the S/R1/R2 segment, where they are allowed to mix for an additional specified amount of time as defined by the assay protocol. Thereafter, the magnetic particles are separated from the S/R1/R2 segment, are transferred to and washed in washes W1 and W1, and are transferred to and reacted with a combination of third and fourth reagents R3/R4. The reaction between the magnetic particles and the combination of third and fourth reagents R3/R4 generates a detectable response in the form of photometric signals which are in proportion to the analyte concentration in the sample S. As noted above, a suitable apparatus for carrying out such an immunoassay is shown in FIG. 1B and includes first and second magnets 60 and luminometer 65. The first magnet 60 is used to transfer the magnetic particles into the S/R1/R2 segment after a specific amount of time, and the second magnet 60 is used to transfer the magnetic particles from the S/R1/R2 segment into washes W1 and W2 and ultimately into the R31R4 segment. The luminometer 65 is used to detect and measure the photons emitted from the segment R3/R4 containing the magnetic particles.
Another well known type of immunoassay is the so-called competitive immunoassay. In the test package for a competitive immunoassay, a mixture of sample and a first reagent S/R1 are separated from a second reagent R2 by a vanish bubble VB. Thus, the sample S and first reagent R1 are preincubated in the analytical line 30 for a fixed period of time before being mixed with the second reagent R2 through operation of the vanish zone 50. Then, the remainder of the method proceeds as described above in connection with the sandwich method.
As will be known by one of skill in the art, in a typical chemistry analysis a mixture of the sample and a first reagent SIR, are separated from a second reagent R2 by a vanish bubble VB. Thus, the sample S and first reagent R1 are pre-incubated in the analytical line 30 for a fixed period of time before being mixed with the second reagent R2 through operation of the vanish zone 50. The chemical reaction between the sample S, reagent R1 and reagent R2 produces a chromofore which absorbs light at a specific wavelength. The light absorption is measured every time a S/R1/R2 segment passes through the Flow Cells 45. Since the light absorption is proportional with the concentration of chromofore, which in turn depends on the amount of the analyte in the sample, the analyte concentration can be determined.
In the systems just described, it is very important to keep the timing of the various analyses, whether it be the chemistry or the immunoassay, very accurate and uniform. In particular, in the chemistry method it is important that all test packages pass the vanish zone and the flow cells at precise and uniform times, and in the immunoassay method it is important that all test packages reach the first magnet and the second magnet (where the magnetic particles are removed from the S/R1/R2 segment, thereby terminating the immunochemical reactions) at very precise and uniform times. In order to achieve and maintain such precise timing, it is necessary for the test packages to be maintained at a uniform and consistent length.
The uniformity among test packages can be adversely effected during the aspiration thereof in the following manner. When a liquid with a high surface tension, such as serum, is aspirated, the thickness of the isolation liquid film in the probe 10 and service loop 15 decreases and a portion of the isolation liquid is displaced and pushed ahead of the segment with the high surface tension. The displacement of oil results in a change in the volume of the probe 10 and service loop 15. As a result, shearing would not occur in the middle of the A1/A3 segment, which normally causes the insertion of small air segments into the analytical line 30, which can result in a substantial decrease in the length of the stream.
In addition, in connection with an immunoassay, it is extremely important for the glowing segment, i.e., the R3/R4 segment mixed with the magnetic particles that is emitting photons, to have a constant velocity as it passes through the luminometer 65. If the velocity is not constant, the dwell time, meaning the length of time the glowing segment spends in the luminometer read head, will vary, and the number of photons counted will be incorrect. For example, if the speed of the stream is lower than it should be, the dwell time will be higher, and more photons will be counted. As a result, the measured light intensity will be overestimated and the results will be distorted.
Moreover, in connection with a chemistry analysis, it is generally desirable to take measurements on a specific predetermined number of test packages at the first flow cell 45 during the forward flow of the stream of test packages in the analytical line 30. If the length of the test packages, and thus the stream, becomes too large, less test packages will be observed during the forward flow of the stream for a given movement of the stream pump 46. If the length of the test packages becomes too small, more test packages will be observed during the forward flow of the stream and there is a higher probability for undesirable merging of adjacent liquid segments inside the vanish zone 50. In addition, if the length of the stream is permitted to vary, the timing at which the test packages reach the flow cells 45 will be thrown off. It is important that the timing be accurate because the accuracy of the measurements to be taken depends on the state of the reactions taking place in the test packages, which in turn depends on the reaction rate.